Thromboembolism: prevention and treatment with vena cava filters.

Mechanical approaches to the prevention of pulmonary thromboembolism have evolved from direct operative procedures to the percutaneous insertion of a variety of filter devices. The longest follow-up experience is with the Greenfield vena caval filter (Medi-Tech, Inc, Watertown, MA), which has a long-term vena caval patency rate of 98% and a recurrent embolism rate of 4%. Alternative filters, such as the Bird's Nest (Cook, Inc, Bloomington, IN), VenaTech (VenaTech, Evanston, IL), and Simon Nitinol (Nitinol Medical Technologies, Woburn, MA), are effective in the prevention of embolism but have a vena caval thrombosis rate of 8% to 20%. The efficacy and safety of prophylactic insertion of the Greenfield filter has been demonstrated in several clinical trials, which appears to justify its use in appropriately selected high-risk patients scheduled for orthopedic procedures.